The gun sounded on NFL Network's sixth season of game coverage Thursday night with the Indianapolis Colts topping the Houston Texans in a thriller.The Thursday Night Football contest, decided when Reggie Wayne hauled in a TD pass with 19 seconds left to give the Colts just their second win of the season and hurt the AFC South champion Texans' playoff positioning, drew 4.58 million viewers, excluding those who watched on over-the-air stations in the participating teams' DMAs, according to Nielsen data.That Dec. 22. delivery was down significantly, 41%,from NFL Network's 2010 season finale: the Arizona Cardinals defeated the Dallas Cowboys 27-26 in front of 7.8 million cable viewers.The Nielsen comparative, though, was not apples-to-apples: last season's game fell on Christmas night and involved America's Team, while the Colts have played all season without meal ticket Peyton Manning. This season, NBC will televise the Green Bay Packers and Chicago Bears on Christmas night -- the only game on the NFL slate on Sunday in deference to the holiday schedule. The bulk of the pro football action in Week 16 takes place on Christmas Eve.